1. Field of the Invention
The invention relates to a circuit arrangement for reproducing audio information signals recorded in one or a normal plurality of audio channels on a movable sound carrier while the sound carrier is moved with a reproduction speed during reproduction, this arrangement comprising a noise reduction circuit and in this arrangement each audio channel having an RC network that includes at least one RC filter.
2. Description of the Related Art
This type of circuit arrangements for reproducing audio information signals recorded on a sound carrier, which arrangements comprise a noise reduction circuit, have gained ground for use in tape recorders, more specifically, cassette recorders. In this example, the movable sound carrier is understood to be a magnetic tape which is moved past a magnetic head whose output signals are applied to the reproduction circuit arrangement comprising a noise reduction circuit. With such a circuit it may be a matter of noise cancellation according to one of the Dolby systems. In these Dolby systems the treble is lowered on the reproduction side to a greater or lesser extent in dependence on its level, so that, more specifically, the tape noise is reduced simultaneously, Such noise reduction circuits require various filters which have different time constants. Therefore, at least one RC network having one or a plurality of RC filters is provided for each audio channel. A great variety of circuits of this type are known.
In addition, circuits are known which are used for recognizing gaps in the audio information signals when the sound carrier has an increased speed relative to the normal reproduction speed. In the above example of the cassette tape recorder this means that the tape is moved e.g. with a rewinding speed while the magnetic head picks up the audio information signals from the tape in a similar manner that it does with the reproduction speed. In this case, however, not the audio information signals as such are to be evaluated, but there should be detected when gaps occur in the audio information signals. In this manner, for example, individual music titles can be located on the tape. Such gap detection circuits are also known in a great variety of embodiments.